We have been able to isolate the cyanobacterium Microcystis aeruginosa from water samples of ponds and river where patients of rhinosporidiosis were bathing. It is likely that this cyanobacterium is the causative agents of this disease. The bluish-green cells of M. aeruginosa also have a colorless small cell stage called nanocyte which has been detected in clear waters of all the pond and river samples studied. Both large cells and nanocytes of M. aeruginosa could be recognized inside the round bodies of rhinosporidiosis by light and electron microscopy. Further work on culturing this organism from excised samples and evaluation for drug therapy are in progress. It is hoped that, if therapy becomes available, no surgery would be required for this disease. It is suggested that the waters from ponds and lakes, as well as municipal and recreational waters, be checked for the nanocyte stage of M. aeruginosa. Etiological controversies of rhinosporidiosis have been reasonably solved. The new findings justify a change in the name "rhinosporidiosis" that had been associated with the fungus Rhinosporidium Seeberi.

The causative agent of rhinosporidiosis is a microscopic round body in polypoidal masses that is believed to be the sporangium of a fungusRhinosporidium seeberi. But fungal aetiology can not be proved with certainty. Attempts to culture the fungus on various media have also been unsuccessful. In a recent study pond water samples, from water in which patients had been bathing, were analysed and a unicellular prokaryotic cyanobacteriumMicrocystis aeruginosawas isolated. The same cyanobacterium was demonstrated in clinical samples from patients with rhinosporidiosis. Consequent to these findings, attempts were made to culture the causative organism of rhinosporidiosis under conditions that support growth of cyanobacteria.This study describes a simple method for laboratory culture of this organism. Observations based on laser-scanning confocal microscopy, light and electron microscopy confirm that a cyanobacterium,Microcystissp. is the causative agent of the disease. Rhinosporidiosis is the first human disease to be shown to be caused by a cyanobacterium. The findings have opened the way for development of therapy.

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